The present invention relates in general to key locks for use in safe deposit box applications and the like, and more particularly to safe deposit box key locks of either the single or double key type, wherein the lock mechanism for the renter key in the single key type, or for the renter key and guard key in the double key type, are capable of being changed in the field for different renter keys or different renter keys and guard keys.
It will be appreciated that safe deposit boxes and bank vaults and similar security installations are successively leased to different parties, to whom the lessor furnishes a renter's key adapted to open a given safe deposit box, in the single key lock application, or wherein the lessor furnishes a renter's key adapted to open a box after being partially operated or armed by a guard or prep key, in the dual key application. Often, lessees or renters fail to return the renter's key at the expiration of their lease, or the renter may lose the renter's key, and it becomes necessary in such cases to change the safe deposit key lock so that it can be operated by a renter's key bit having a different configuration. Also, even if the lessee or renter returns the renter's key at the expiration of his lease, it is desirable to change the key bit configuration to which the lock is responsive whenever the renter of the box is changed, to prevent the otherwise possible use of an unauthorized duplicate of the renter's key which may have been made before the renter's key was returned.
For this reason, certain safe deposit locks have been made in such a manner that the position of the gatings in the tumblers operated by the renter's key is changeable (or wherein the tumblers for both the renter's key and the guard key are changeable) so that the position of the gatings may be adjustably set to be opened by a different renter's key (or guard key). The typical practice in this regard has been to provide a change key in the form of a non-round cross-section rod which is insertable into an opening in the safe deposit lock case or rear cover wall and through shaped openings in the renter's key tumbler, when the safe deposit lock has been activated by the old renter's key. Typically, the tumblers have either been of the pivoted type or of the slide type. In the case of the pivoted type, the combination change key interfits into shaped openings in one of two pivoted companion tumbler sectors for each renter's key tumbler lever, to decouple normally mated tumbler lever sections from the key tumblers and permit them to recouple in a position corresponding to the configuration of the bit of the new renter's key. In the case of the slide tumbler type construction, clamping post type structures have been provided to normally clamp slidable key tumblers in various combination positions, and to permit selective release of the slidable key tumblers under predetermined circumstances to permit readjustment of their relative positions.
It has become recognized that it is also desirable to provide for the setting of the guard key or prep key tumbler lever system in accordance with different guard key or prep key configurations, so that the guard key to be used with safe deposit locks can be changed from time to time to provide greater security or reset the locks when the guard key is lost or when change of guard personnel occurs. Attempts to provide for changing the lock to accommodate different guard keys as well as different renter's keys have generally involved use of renter key tumbler levers which are either made-up of two pivoted companion tumbler sectors which may be selectively decoupled when the lock is in a change mode to permit relative adjustment of one of the tumbler sectors with respect to the other to accommodate the configuration of the bit of the new renter's key, and also using a entirely different set of guard key tumbler levers disposed in a portion of the lock housing spaced from the renter's key tumbler levers and a plurality of independently adjustable fence members associated with the guard key tumblers capable of being set to different positions to operate with different guard key configurations. Such a ccnstruction requires a considerably large space-consuming lock configuration and considerable increased complications and expense in the assembly of safe deposit locks.
An object of the present invention is the provision of a novel changeable safe deposit lock, usable in a single key or a double key configuration, wherein a changing screw is provided which must be loosened in the back of the lock after insertion of a key for which the lock is presently conditioned and rotation of the key to the unlocked condition, to allow the key to be rotated an additional distance so that the head of the changing screw becomes positioned in a different position above a shelf formation in the back of the lock case, whereupon, after removal of the initial key, a second key may be placed in the changing position slot, rotated to the forward direction to come to a physical stop, and the changing screw is then engaged with the case in the forward position where it can be tightened down to lock the fences in the new position adapted to the new key.
Other objects, advantages and capabilities of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the present invention.